<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <meta http-equiv="X-UA-Compatible" content="ie=edge">
  <title>trim方法</title>
</head>

<body>
  <input type="text"> <button>点击</button>
  <div></div>
  <script>
    // trim 方法去除字符串两侧空格
    // var str = '   an  dy   ';
    // console.log(str);//   an  dy   
    // var str1 = str.trim();
    // console.log(str1); //an  dy


    var input = document.querySelector('input');
    var btn = document.querySelector('button');
    var div = document.querySelector('div');
    btn.onclick = function () {
      var str = input.value.trim();
      if (str === '') {
        alert('请输入内容');
      } else {
        console.log(str);
        console.log(str.length);
        div.innerHTML = str;
      }
    }
  </script>
</body>

</html>